Cervicometer



Feb. 9, 1960 VON MICSKYY 2,924,220

CERVICOMETER Filed Feb. 20, 1959 v 5 Sheets-Sheet 1 FIG. I.

\ INVENTOR ll LAJOS I. VON MICSKY ATTORNEY Feb. 9, 1960 L. 1. VON MICSKY2,924,220

CERVICOMETER Filed Feb. 20, 1959 5 Sheets-Sheet 2 FIG. 2.

INVEN'i'OR LAJOS I. VON MICSKY ATTO R N EY L. l. VON MICSKY CERVI COMETER Feb. 9, 1960 5 Sheets-Sheet s 9. CALIBR 8i- Filed Feb. 20, 1959FIG.

Feb. 9, 1960 Filed Feb. 20, 1959 L. l. VON MICSKY CERVICOMETER ISJNEA ca (u v POWER TRANSDUCER SUPPLY (RHEOSTAT) GRAPHIC (TRANSFORMER) RECORDEROR OPTICAL ASSEMBLY FIRST VOLTAGE AMPLIFIER REGULATOR SOLENOIDCALIBRATOR AUDBLE ALARM MONWOR 331* FIG. I I.

L ELECTRONIC CONTROL 2 CIRCUIT \NVENTOR LAJOS I. VON MICSKY gMW AT ORNEYFeb. 9, 1960 Filed Feb. 20, 1959 L. I. VON MICSKY 2,924,220

CERVICOMETER FIG. I2.

5 Sheets-Sheet 5 INVENTOR- LAJOS l. VON MICSKY ATTORNEY 1C Patented Feb.9, 1960 CERVICONIETER Lajos I. Von Micsky, Mayaguez, Puerto RicoApplication February 20, 1959, Serial No. 794,658 9 Claims. (Cl. 128361)This invention relates to an obstetrical instrument. More particularly,it is directed to be an electronic cervicometer for measuring,registering, recording and signaling dilation of the cervix uteri inchildbirth.

During labor it is important to know the extent and progress of dilationof the cervix. At the present time this information is obtained by meansof digital examinations which are taken at periodic or random intervals.The attending physician utilizes the vaginal or rectal route. Themeasurements thus obtained are expressed in terms of the number offingers which may be inserted into the cervix, or in centimeters,estimated by palpating the opposite rims of the cervix with a fingerintroduced into the rectum. This procedure has several disadvan tag'es.It is at best haphazard and constitutes nothing more than a spotchecking of a continuous progressive development. This producesinaccurate results, and the margin of error varies in accordance withthe skill and experience of the person taking the measurements.Moreover, the measurements cannot be defined with such exactitude as toenable one person (the attending nurse) to report them accurately toanother (the attending physician). Aside from the foregoing, digitalexamination produces considerable discomfort and even pain to thepatient and it is unsatisfactory in many other respects known to thosewho practice and experience the method.

The main object of this invention is to provide acombinedelectro-mechanical and electronic device "of the character described,which will continuously and accurately measure the extent of cervicaldilation and register the same precisely and clearly in such a manner asto enable the attending physician or nurse to take progress readings atprescribed intervals, or record the progress of dilation continuouslyduring the entire labor. By' the use of this device the human error iseliminated both in the taking and communication of such measurements.

Another object of this invention is 'to provide acornpact, rugged, andsterilizable electro-mechanical instrument of the character describedwhich maybe carried into the patients vagina and attached to the cervixby needles Without pain or injury to the patient.

A further object of this invention is to provide a combinedelectro-mechanical and electronic device which, in addition to measuringand registering the mutton of cervix, provides means for signalingthe'attending nurse or physician when the desired extent of dilation isobtained. v I

The signaling means may give audible or visible signals in the immediatevicinity of the patient or may be communicated to other stations orlocations in the hos pital where the device is used. With this featurethere is no need to watch continuously the registering instruments. Itsuflices merely to check the reading from time to time, and to relyultimately upon the signaling means for adequate notice of'completion ofthe desired dilation. Another object of the invention is to provide acombined electro-me'chanical and electronic device of the characterdescribed, which in addition to measuring,

registering, recording and signaling the dilation of the.

cervix, incorporates safety features for the protection of the motherand child.

One of these safety features is the automatic retrac= tion of needlesfrom cervical tissue upon completion of the desired extent of dilation.This feature is intended to protect the patient and child against thecontingency, of the attending nurse or physician being occupiedelsewhere at the time when dilation is completed. It also'will be asafety factor in cases of pathologically rapid de liveries, so-calledprecipitate deliveries. t

The other feature to protect the patientis a safety circuit. Should thecontrol fail to maintain proper voltage, said safety circuit will switchon a safety light and automatically remove all voltage from thetransducer and registering circuits, eliminating thereby all danger ofelectrical shock to mother and child.

Still another object of this invention is to provide a registeringinstrument of the character described which as a result of propercombination of its optical and electrical components, will allow notonly registering the extent of the cervical dilation but alsovisualization of cervical movements.

The potential uses of the instrument herein described and claimed aremanifold. It is intended for clinical use in connection with individualpatients. It is, however, also useful as an academic tool for objectivestudy of labor forces as reflected by cervical dilation, and for thestudy of the effect on labor 'of such various factors as drugs,anesthetics, hormones, hypnosis and psychosomatic influence.

Other objects and advantages of this invention will in part be obviousand in part be hereafter pointed out.

The electronic cervicometer herein described and claimed comprisesseveral major component parts, each with a specific function. Theircombined and correlated operation is the function of the entire deviceas -a unit which can be briefly stated as follows:

The intravaginally applied electro-mechanical instrument, best describedas a transducer caliper, is provided with a pair of lever arms which atone end are detachab'ly secured by needles to the opposite rims of thecervix, and at the other end are connected to a potentiometer to which asmall voltage is applied. As the cervix dilates, the angular distancebetween its arms increases but because of a translatory movement of thepivot point of the lever arms of the instrument, the voltage output isnon-linear with respect to the dilation (distance between oppositepoints of cervical rim). This voltage is applied to an electronic unit,the amplifier tubes of which are based in such a way that they willcompensate for the non-linear input from the potentiometer and providelinear current for the registering instruments. Saidunit will alsooperate a signaling circuit and the electric release mechanism for theautomatic retraction of the tissue-engaging needles.

The registering instruments which can be used separately orsimultaneously are of various types, each serving a different purpose. Acalibrated milliammeter servesfor indicating cervicial dilation incentimeters. optical assembly permits visualization of cervical movements besides providing measurement. A graphic recorder will rendercontinuous graphs on the progress of cervical dilation during entirelabor.

The invention is illustrated in'the accompanying drawing in which:

Fig. 1 is an anteroposterior anatomical view of the pelvic region duringthe process of labor "showing the herein described and claimedtransducer caliper in situ (inserted into the vagina andfits wa"attached by tissue engagin'g'needlesto the opposite rims of "the cervixat 3:00 and 9:00 oclock, respectively).

vided with two curves, a cephalic curve in the frontal -Fig.- 2 is alateral anatomical view (90 degrees removed from the view of Fig. 1showing transducer caliper in situ). i

Fig. 3 is partly exploded, partly sectional view of one of the arms ofthe transducer caliper with the cable as semblyand extension bar. 1 i

Fig. 4 is a cross-sectional view-on the line 4-4 of Fig.3. i a

Fig." 5 is an enlarged fragmentary longitudinal section on the line 5 -5of Fig. 3 showing the details 'of the socket portion of one of the armsof the transducer ca Fig. 6 is an enlarged sectional view through thepotentiometer and its cylindrical housing of the transducer I caliper. r

Fig. 7 is afragm'entary sectional view through the automatic releasemechanism which automatically retracts needles from the cervical tissueswhen dilation is completed.- V v Fig. 8 is a sectional view on theline-of 88 of Fig. 7.

Fig. 9 is a sectional view on the line 99 of Fig. 7.

Fig. 10 is a block diagram of the electronic unit and its correlation tothe rest of the electrical components of the electronic cervicometer.

Fig. 11 is-a schematic drawing of an optical assembly which may be'usedin connection with the basic invention herein claimed, said opticalassembly being adapted to V where said lips or rims are designated bythereference number 15.

provide accurate measurements and visualization of cer- V vicalmovements on a calibrated ground glass screen.

Fig. 12 is a geometrical representation of the transducer caliper.

Fig. 13 is the circuit diagram of the cervicometer in its simplest formcomposed only of a transducer caliper in a circuit with a dry cell andwith a milliammeter which is empirically calibrated in terms of distancein order to compensate for the non-linear voltage output of thetransducer caliper.

Fig. 14 is a schematic representation of the sliding ring contactor andthe parts of the cylindrical casing on which it is mounted. The partssupporting the wiper springs are represented in the lateral view; thosesupporting the contactor rings are represented in the front view.

Referring more particularly to the accompanying drawings in which thecorresponding parts are indicated by identical characters of referencein the several figures it can be seen on Figures 1, 2, 3 and 5 that theintravaginally applied electromechanic instrument designated from now onas a transducer caliper is composed of the fOHOW'. ing major parts:

(1)' A pair of lever arms 10 for the mechanical trans mission of themovements of the cervix to the pivoted and fixed elements of apotentiometer.

(2) A pair of needles 12 extending through socket portion of said armsfor securing them to the cervix.

(3) A cable assembly 25 for remote control of needles.

(4) A potentiometer in a waterproof housing 112.to which said'arms areconnected.

The arms 10 are made of stainless steel and are proplane and a pelviccurve in the sagittal plane. The cephalic curve 16 corresponds to theoutline of the fetal head and serves to prevent distortions in readingsat dilations greater than 6 cm. The pelvic curve 17 corresponds to thepelvic axis and serves to eliminate distortions which would arisebecause of specific anatomical condi tions, if the curved nature of thepelvic axis were not to be taken into consideration inthe design of thearms. The cephalic curve can best be seen on Fig. 1 and the pelvic curveon Figs. 2 and 3.

Each of the arms is provided at theforward end with asocket portion 11.The socket portion has a socket cavity 19 which is adapted to receivethe opposite lips or rims of the cervix. This. Gill b be seen in Fig 1,

It can be observed that thesocket portion of each arm is provided withan elongated compartment 18 extending longitudinally. Two small slits 20at the forward end of said compartment 18 provide communication betweensaid compartment and the socket cavity. The pointed forward end of apair of needles 12 projects through the.

said slits 20 into the socket cavity. It will be seen n Fig. 5 that intheirretractedjposition (indicated by solld lines) the needles aredisposed within1said compartment 18 and in their projected position(indicated by broken lines) said needles extend into the socket cavity.A slot or recess 23 situated on a ball pointed projection of the socketportionperforms the function of receiving the needle points to protectthe surrounding tissues from injury.

The base or back of the needles is supported on a block 22 which isslidably mounted within compartment 18 said block is provided with ahole 24 which is generally coaxial with the needles 12,. and projectinginto ment with a screw 32 provides a water-proof closure for compartment18. The-cover platejmay be removed to expose the several componentsabovementioned which are enclosed within said compartment, allowing forthe change of needles, a thorough cleaning, and submergedsterilization-of the compartment 18.

as I

in :a tubular shank 27 which is provided at its lower end Thesocketportion of the arm ust described continues with an opening 101 throughwhich the cable 261inc0rporated in a flexible tube;34 is introduced tobe C0111 nected to aforementioned block 22. At its lower end adjacent toopening 101 the tubular shank is also provided with a-boss 102 whichfits into rectangular sockets 156-158 of lugs 152--154'of sliding rings140-142..

These sliding rings are part ofthe housing of the potentiometer-to bedescribed later. On the side of the boss a spring clip is mounted in agroove and fits into a slot 151 on the side of lugs 152154 attachingthereby the arms to said sliding rings -142. Boss 102 is also providedwith a lip 107 which when the arms are connected to sliding rings restson the top .part of the 1 lug-and together with the spring-cliplockssaid boss into rectangular socket of lug. i

The transducer caliper is designed as slim as possible and its parts areso proportioned that when the arms are in zero position. (the twoball-pointed projections of socket portion resting against each other)the width of i the whole instrument is less than that of two fingersused. in course of routine pelvic examinations. The projected lengths ofthe from the boss to slits 20 in socket cavity is 7 cm. The overalllength due to the pelvic and cephalic curve is somewhat more.

The cable assembly comprises i a cable 26? slidably mounted within aflexibletube 34, an actuating button 42, a coil compression springtoeffectretraction of cable; a'lock 37 i and a releasebutton 60 with itstubular shaft 62. Cable 26 at its forwardend is fixed by said screw 2810block 22 and flexible tube 34 is secured at its forward end by a screwthreaded engagement to a sleeve 36 mounted-withincompartment18. Theforward or upper third of cable and flexible tube is housed inside of atubular shank of arms. The. outer or lower end of the-tube 34is-providedwith an enlarged portion 38,

housing -a coil spring 50 to .eifect retraction of cable.

. .5 26 projects through enlargement 38 and housing 40 and is providedat its outer end with an actuating button 42.

A ring 44 is welded to wire or cable 26 enclosed in enlargement 38. Saidenlargement is provided at its forward end with an annular shoulder 46and it is also provided at its back end with an annular flange 48. Acoiled compression spring 50 encircles cable 26 within enlargement 38;one end of said spring bearing against shoulder 46 and the opposite endbearing against ring 44. Since said ring is secured to cable 26, theeffect of this arrangement is to cause said wire to be springurged inrearward direction (downwardly as viewed in Fig. 9). Flange 48 serves asa stop to ring 44. Since needle 12 is secured to block 22 and since saidblock is secured to the forward end of wire 26, the net effect of theforegoing is to cause retraction of said needle to its solid lineposition shown in Fig. 5.

Further reference to Fig. 9 will disclose the fact that a lock 37 isprovided to hold wire 26 in any selected forward position against theaction of spring 59. When button 42 is manually pushed to move wire 26forward in order to cause needles 12 to engage the cervical tissue, suchforward movement takes place against the action of spring 50 and causessaid spring to load. It will now be observed that housing 40 is providedwith a generally tapered or conical end wall 52 and with a plurality ofballs 54 seated against said tapered wall. A coiled compression spring56 bears at one end against the front wall 58 of housing 40 and at itsopposite end against balls 54. The halls are therefore wedged betweenthe tapered wall and wire 26 and this in turn locks the wire against theaction of spring 50.

Fig. 1 shows arms in engagement with the cervical lips and needles 12transpiercing said lips to prevent dislodgment of said arms from saidlips. Wires 26 would thus be positioned in their forward positionagainst the action of springs 50. When it is desired to disengageneedles from the cervical lips, release buttons 60 are actuated, eithermanually or by means hereinafter described. Referring again to Fig. 9 itwill be observed that each release button 60 is provided with tubularshank 62 through which wire 26 extends. The forward end of shank 62passes through an opening 64 at the back end of housing 40. Said tubularshank is provided with an enlarged end portion 66 which prevents it frombeing pulled out of said opening 64. Enlarged end portion 66 of saidshank 62 performs the additional function of engaging balls 54 in orderto release them from wire 26. Such release occurs when release button 60is pushed forwardly (upwardly as viewed in Fig. 9) and balls 54 arethereby moved out of wedging relation between the Wire 26 on the onehand and the tapered end wall 52 on the other hand. Spring 50 is therebyrendered free to re tract wire 26 and with it the needles 12.

As has been above stated this procedure may be performed manually or byother means and reference is now made to Figs. 7 and 8 for showing anelectro-rnechanical apparatus for accomplishing this result.

A casing 70 provided with two spring-urged hinged covers 100 is mountedon a belt which may be placed around the thigh of the patient and isheld in place by suitable fastening means such as buckle 74. A solenoid76 is mounted within said casing 70 between the two compartments 84 and86 which are of such dimensions and shape that they will accommodate theenlarged portions 38 and housing 40 of the two cable assemblies abovementioned. These in turn are held in compartments 84 and 86 by pressureof spring urged covers 100. A preferred type of lock 95 mounted on topof casing, secures the covers in their closed position. The solenoid isprovided with'a coil 78 and a' plunger 80 in the conventional manner. Abridge 82 is secured at its center to the plunger and; its ends are ;-incontact with the. release buttons 60. When the solenoid is energized,plunger 80 is retracted into the coils and bridge 82 is 6 thereby causedto actuate the release buttons, causing these latters to release wires26 from their respective locking balls 54. Springs 56) are therebyreleased sufficiently to enable them to retract wires 26 and needles 12connected therewith.

The mechanism shown in Fig. 7 may also be operated manually. A tubularstem 90 is provided on casing 70 and a hole is provided in the wall ofsaid casing to provide communication between said tubular stem 90 andthe inside of the casing. At the outer end of said tubular stem is a cup92 adapted to receive a button 94 and a compression spring 96. Attachedto said button is a shank 98 which extends through tubular stem 90 andinto engagement with bridge 82. When button 94 is pressed against theaction of spring 96 shank 98, acting through bridge 82 actuates the tworelease buttons 60 without the intervention of the solenoid.

Two receptacles 81 and 83 are provided on casing 70 to receive plugs 87and 89 respectively. As it is apparent from Fig. 7 conductors 180 and186 incorporated in cable 189 Will continue in cable 191 toward thefirst amplifier. Cable 191 incorporates two more conductors whichconnect solenoid 76 to the calibrator. The purpose of this arrangementis to permit disconnection of different units of the device for, easierhandling and to eliminate a maze of cables entangling each other.

The structural features shown in Figs. 7 and 8 are not critical and maybe modified as desired. It is of course understood that, upon the adventor approach or" full dilation the attending physician will himselfdisengage the apparatus from the cervix, and it is intended that theapparatus be used in this manner. The automatic operation abovedescribed, wherein the solenoid disengages the apparatus from thetissues of thepatient, is intended mainly for precautionary purposes, toavoid risk of injury to the patient or to the fetus should the physicianhappen not to be in attendance at themoment of full dilation.

Turning now to Fig. 1 it will be noted that, although the dimensions ofthe transducer caliper were reduced to the smallest possible size thecylindrical casing 112 of the potentiometer is still too bulky to allowthe attachments of the arms to the cervix under vision without usinglarge vaginal retractors and applying on them such a force that wouldcause considerable pain to the patient. In order to solve this problemthe apparatus was so devised that the arms are detachably fixed by aspring clip into rectangular-sockets 158156 of sliding rings 140 142 ofcylindrical casing 112, allowing thereby the separate introduction ofthe arms and the cylindrical casing 112 into the vagina. To facilitatethe attachment of the relatively short arms to the cervical tissue anextension bar 108 was devised, mounted within sleeve 119. One suchextension bar is shown in Figs. 3 and 4. It will there be seen that theboss 102 mounted at the back end of each arm 10 has a quadrangularprojection 103 which has the same dimensions as the extension bar 108.This quadrangular projection has a threaded socket 1M which is adaptedto receive the threaded end 136 of the extension bar 168. The extensionbar is attached to the arm 10 by screwing the threaded end 1% of saidbar 1&8 into threaded socket 104 of boss 102 and sliding the sleeve 11%over quadrangular projection 16-3 of boss. It is by means of saidextension bar that arm 10 may be guided into operative position relativeto the cervix of the patient. 4

This procedure which is actually a minor obstetrical operation iscarried out observing the rules of aseptic technique. The transducercaliper with the arms detached from the cylindrical casing and theextension bars are sterilized by submerging them for 15 min. into C.I.R.(or other similar) sterilizing solution. The patient is placed inlithotomy position and after a surgical perneal preparation she isdraped and the cervix is exposed-by the means of vaginal retractors. Theextension bars are attached to the arms and, using the bar as a handle,the left arm is introduced to the vagina and placed so that theballpointed projection of the socket portion will be inserted into thecervical canal and. the portionof the rim corresponding to 3:00 oclockwill be accommodated in the socket cavity. Now by pressing the actuatingbutton 42 of cable assembly the needles will transpierce the cervicaltissue and securely attach the lever arms to the cervix. As'it can be'seen on Fig. 3 two needles are supported on each needle block 22. Theplurality of needles diminishes the possibility that the needlesgetseparated from cervical tissue and the arms dislodged in the course oflabor. Since the pain perception of the cervix is negligible noanaesthesia will be required for this procedure and due to the size ofneedles the'trauma inflicted is inconsequential.

By slipping rectangular sockets 156-158 over boss 102 spring clip 105will engage into slot 151 of lugs 152- 154 fixing thereby the armsfirmly to the cylindrical casing 112. Now the extension bars can bedetached by sliding sleeve 110 backwards and unscrewing extension bar108 from the threaded socket 104 of boss 102. Now the electric releasemechanism for automatic release of tissue engaging needles is fastenedby the rubber belt to the patients thigh, the hinged doors are opened,the proper position of bridge 82 checked and enlarged portion 38 andhousing 40 of lock 37 will be placed in their corresponding compartment.

The foregoing description relates to the mechanical parts of the presentinvention. The following description will cover its electricalcomponents in combination with such additional mechanical parts as areassociated with it.

It has been stated that arms 10 are connected to a potentiometer 132.Said potentiometer is best shown in Fig. 6 and it will be observed thatit includes a cylindrical casing 112. Said casing encloses a sleeve 114which sup-,

ports a pair of end-bearing plates 116 and 118, respectively; Hubs 120and 122 of said end-bearing plates support shafts 124 and 126,respectively. Stud shaft 124 supports a bracket 130 which enclosespotentiometer 132. Shaft 126 extends through a fixed collar 134 and isconnected to the movable contact element or wiper which engages theresistance element or coil of the potentiometer. It will be understoodthat as in all potentiometers it is immaterial whether the coil orresistance moves relative to the wiper or whether the wiper movesrelative to the coil or resistance, or whether both move relative toeach other.

Casing 112 comprises, in efiect a pair of spaced shells 113 and 115which are secured to the inner sleeve 114. Between the two shells is toa pair of rings 140 and 142 respectively, these rings being mounted onsaid inner sleeve 114for rotatory movement relative to each other andrelative to said inner sleeve about a common axis coinciding with theaxis of shafts 124 and 126. These shafts are also coaxial with thepotentiometers coil or resistance and the potentiometers wiper.

The various componet parts of the casing are constructed and fitted withsuch accuracy that the waterproofing indispensable for the protection ofthe potentiometer is accomplished alone by the precision fit, renderingunnecessary the use of rubber washers. The casing as well as the leverarms are made of stainless steel of 0.020 thickness which, whileassuring great strucural strength, will not make the instrument heavyand will resist the corrosive action of the sterilizing solutions.

Slots 144 and 146 are provided in sleeve 114 and through said slotsmechanical arms 148 and 150 provide transmission of movements betweenpotentiometer and said rings 140- 142. Mechanical arm 150 at one end isconnected to shaft. 126 of the potentiometer; at the other end itprojects into a hole 164 of lug 154 which is located inwardly torectangular socket 158. Mechanical arm 148 has a small base plate 160which is compressed between the potentiometer andbracket- 130; its.other end projectsinto a hole'162 inlug ,l52 inwardly from rec; tangularsocket 156. Ring142 is 'therebyconnected'to the potentiometerswiper andring 140 to the potentiometers coil. Itis evident fromthisdescriptionthat when either of said rings is moved relatively to theotherring, relative movementswill take place'between the 'coil and wiperof the potentiometer. The bracket supporting the potentiometer containstwo contactor rings 196 and 198, each connected toa terminal ofpotentiometer 132 and mounted on insulatingdisc 195. Since there are.three connections necessary for the potentiometercircuitthe. thirdconnection terminal 194 would be carried directly to the metal casing ofthe potentiometer. When the, potentiometer is installed'within itscasing the two con-j tactor rings will make contact with the two wipersprings 197 and 199, respectively. These are mounted on in-f sula tingdisc 193, which is supported by end-bearing plate 116. The wiper springsare connected to conductors 180 and 186 respectively, which areincorporated into cable 189 and leave the casing through opening 185located on spaced shell 115. Waterproofing is established by theemployment of a small rubber Washer 187 fitting into opening 185.

Due to its particular construction the previously de-, scribedinstrument has three distinctive characteristics when in operation. (1)The lever arms are conneced to sliding rings 140 and 142, respectively.These areso situated on sleeve 114 that theyrotate around it coaxiallywith thepotentiometer. For that reason when the arms attached to thecervix are moved apart due to the, dilation of the cervix, theirmovements will be angular about the axis of the potentiometer and alwaystangent to its cylindrical casing. (2) In the operational position thearms of the instrumentare attached by needles to the cervix. The resultof this arrangement is that when the dilating cervix moves the armsapart, with the increase of angle between said arms the pivot point(axisfof potentiometer) moves closer to the line between the attachmentpoints (distance to be determined).

e (3) The movements of the sliding rings are transmitted bymechanical-arms to. the potentiometers coil and wiper, respectively. Itfollows that when the arms move apart their angular movement will causea relative movement between the potentiometers coil and wiper,

resulting in a variation 'of voltage output caused by the change ofresistance of, said potentiometer.

Consequently when using the electronic cervicometer the dilation of thecervix (linear distance between opposite points 'of cervical rim) isdetermined by measuring the change of angle between the arms as it isreflected by a variation in voltageioutput. It will now be apparent thatthe electronic cervicometer in accordance with the invention utilizesthe relation between the angle and distance for measuring the unknowndistance between opposite points of the rim of the cervix.

Fig. 12 is a geometrical representation of the transducercaliper. (Theoutlines of the instrument are drawn on the left side of diagramforidentification of the instruments geometrically represented components.)On this figure w denotes thedistance measured; Y is the length of leverarm; A representsthe axis of potentiometer; r is the radius of slidingring and 0 is the half angle of turn of wiper of potentiometer relativeto its coil.

(5) E=IR 6 w e m E 201 S111 2 It appears from the above equations that wdoes not vary directly with 0. Substituting values; r=1 cm., y- 7 cm.into Equation 3, and assigning values from 1 to 14 to w, a curve 0 vs. wcan be plotted. This proves to'be a non-linear curve. Since the changeof resistance and so the variation in voltage output depends on 0, itfollows that the voltage output from the transducer will be nonlinear. Amilliammeter in circuit with the transducer can be calibrated in termsof distance for accurate indication of cervical dilation, but therecorder and also the aforementioned optical assembly require linearcurrent. For that reason a correction should be made to compensate forthe non-linear voltage input from the potentiometer. This can beobtained by selecting an amplifier tube for the electronic tmit, thecharacteristic curve of which is approximately the mirror image of thenon-linear, mathematically determined curve, and by applying the properbias to said amplifier vacuum tubes. Another possible solution is to usea non-linear potentiometer, designed in such a way that it wouldcompensate adequately for the non-linear relation between w and 0 andthus provide a linear voltage output.

Cervicometers composed of only a transducer caliper, a simple circuitwith a dry cell, and an impirically calibrated milliammeter can be madevery compact and inexpensive. Although they lack a great number offeatures of the electronic cervicometer they will constitute a veryuseful and practical clinical instrument.

Fig. 13 illustrates the circuit diagram of such a device. As shown onthis figure the fixed resistance 174 lies across conductors 176 and 178which are connected to the milliammeter 168. Conductor 176 connects oneside of the milliammeter to dry cell 170. Conductor 178 connects theopposite side of the milliammeter to resistance 172 and anotherconductor 180 is connected to the movable contact member 182 of saidresistance 172. It will noW be noted that conductor 180 is connected toa terminal or contact member 184 and another conductor 186 connects thedry cell 170 to a second terminal or contact member 188. A pair ofconductors 190 and 190 are plugged into or otherwise connected to theterminals 184 and 188 and one of said conductors is connected to thecoil 132a of potentiometer 118, while the other is connected to thewiper 132b of said potentiometer.

Referring now to Fig. it shows the electronic unit in correlation withthe rest of the electrical system of the device.

As it is apparent from this illustration the non-linear variation of thetransducer is amplified through an electronic amplifier designated asFirst amplifier. Since a linear current is required to operate therecorder or optical assembly, designated Graphic recorder and Opticalassembly, respectively, in Fig. 10, it is necessary to compensate forthe non-linear output of the potentiometer by applying proper bias tothe amplifiers. The first amplifier is biased so as to give a linearvoltage output to the directly coupled calibrator. The calibrator isbiased in such manner as to provide linear current output to therecorder circuit.

There are two relays in the plate circuit of the calibrator, one athermal 'relay operating thirty seconds" the power switch is closed.This .delay serves to pro} tect the graphic recorder from any possiblesurge dur= ing the warm-up period of the vacuum tubes. The second relayperforms the following functions: It re-, moves all power from therecorder when it has reached its full scale indication; it operates asmall solenoid (as shown in Fig. 7 of the drawing) which retracts thetissue-engaging needles from the cervix; and it provides a closedcircuit for operation of an optional external alarm, designated Audibleor Visual alarm in Fig. 10 of the drawing. Power is supplied to thepotentiometer and amplifiers by a full wave, transformer operated powersupply. Isolation from the main power line is provided by thetransformer. Proper filtering is obtained with a condenser input filtersystem. Since the entire accuracy of the present device is dependentupon the voltage applied to the potentiometer, a gas voltage regulatortube is used to maintain a constant voltage. This is indicated in Fig.10 of the drawing as the Voltage regulator. I

The safety circuit consists of a relay that is bridged to the voltageregulator tube of the power supply. A safety light designated as such inFig. 10 will glow upon failure of the control to maintain a propervoltage at the regulator tube. The safety circuit will, at the sametime, remove voltage from the potentiometer and registering circuits,thus removing any danger to the patient or the graphic recorder. Agraphic recordercan be attached to the electronic unit to obtain apermanent record of the dilation of the cervix as a function of time.This could be useful for the research purposes specified in the generaldescription of the apparatus.

Referring now to Fig. 11 it illustrates a registering instrument whichby the propercombination of optical and electronic components, andarrangements of parts will allow not only the measurements of cervicaldilation but also visualization of cervical movements.

At it is apparent from the diagram the linear current of the calibratoris introduced into a network 208 to provide the specified proper currentfor the commercially available automatic iris 210 which is placedbetween a condenser 202 and a projection lens 204. An accuratelyproportional dilation of the automatic iris will correspond to anydegree of dilation of the cervix. Using a proper light source 200 and aproper lens-screen distance, life-size image of the cervix can beprojected on a calibrated ground glass screen 206 and all changes incervical movements can be visually followed and measured. A blower 212will provide the cooling system for this optical electronic assembly.The input terminal 214 is to be connected to a conventional voltalternating current household line.

The usefulness of the combined electronic optical assembly is notlimited to the visualization of cervical movements, but with a propertransducer it canbe utilized for the visualization of the movements ofother sphincters or organs with circular musculature.

It will be thus concluded that the described apparatus is a device inwhich the several objects of this invention are achieved and which iswell adapted to'meet the conditions of pratical use.

It will, of course, be understood that various changes in details ofconstruction and arrangements of parts may be made without departingfrom the spirit of the invention and the broad scope of the claims.

I claim:

1. A cervicometer of the character described, comprising a pair of armswhich are adapted to be inserted into the human vagina, fastening meansat the forward ends of said arms to detachably connect them to theopposite lips of the human cervix, a rheostat having a fixed element anda pivoted element, the outer end of one of said arms being connected tosaid fixed element and the outer end of the other arm being connected tosaid pivoted element, a milliamm'eter and a source oielectric current incircuit withsaid rheostatrand-said milliammeter, wherebydilzition ofthe, cervix causes thearms to move apartand the pivoted 'elementof therheostat to pivot relative to the fixed element thereof and thereby tocause'a-change in the reading of the milliammeter proportionate ,to theextent of dilation of the cervix.

2. A cervicometer in accordance with claim 1, wherein the, arms, areprovided at their innerends with socket portions adapted, to receive thelips of the cervix, the fastening.- means by which said arms are adaptedto be attached to said lips comprising a pair of curved needles, one foreach arm, said needles being spring-urged forwardly across .said socketsand being provided with means for retracting them against said springaction. 3. A cervicometer, in accordance with claim 1, wherein the outerends of the arms are connected to the fixed and pivoted elements of therheostat by means of tubular members,- said tubular members beingsecured, respectively, to said fixed and pivoted elements, and saidouter ends of the arms being disposed Within said tubular members, latchmeans being provided between said outer ends of the arms on the one handand the tubular members on I v. the other hand, to detachably securesaid outer ends of the arms to said tubular members.

4. A cervicometer in accordance with claim 3 wherein a hollow housing isprovided for the rheostat, said tubular members being disposed mainlywithin said hollow hous through which end portions of said tubularmembers project, said slots being adapted to permit relative pivotalmovement between the two tubular members.

5. A cervicometer in accordance with claim 1, which is. providedwithsupporting means forsupportiug it upon one of the thighs" of thepatient, automatic release means beingprovided'which is sensitive to thespacing of the arms and which releases the fastening mean son said armsfrom the cervical lips when dilation attains a predeter mined degree. i

6. A cervicometer in accordancewith claim 5, wherein the, automaticrelease means includes a solenoid which is electrically connected to therheostat, said rheostat controlling the currentwhich reaches thesolenoidso as to actuate the solenoid at a predetermined time related to theprogressof dilation. V

7. A cervicometer in accordance with claim 1, wherein an audible alarmwhich is electrically actuated is connected to the rheostat, so as tosignal full dilation to the attending medical personnel.

-8. A cervicometer inaccordance with claim 1, wherein 1,856,295 SovatkinMay 3, 1932 2,456,806 Wolfie Dec. 21, 1948 2,858,826 Kahn Nov. 4, 19582,886,892 Banfill, May 19, 1959 e medal

